Why do some of my Google calendar events show in my calendar & some don't?

This is quite frustrating and I can't seem to find a solution to this. I have birthdays and anniversaries entered for my contacts which are sync'd to my phone as well. Most of the birthdays and anniversaries show up in my calendar on my phone but some don't. Doesn't appear to be any rhyme or reason to it either. I noticed that on my HTC Evo LTE I can go to Calendar and specify which calendars it displays. Inside here there is the 'Contacts birthday's & Events' like what I have displayed on my Google Calendar on my PC and the color is yellow. The interesting part is that there is another calendar option called 'People' that is green and I think is an HTC Sense thing but am not 100% on this. The interesting part is that if I choose to display this all of my contact's dates are displayed in duplicate but some extra ones also display.. the ones that don't display on my yellow calendar. One might think the simple solution would be to uncheck the yellow one and check the green one and be done with it but there are also dates that show up on the yellow calendar that don't show up on the green one. The weird part is they BOTH take info from the same source so I don't understand this difference. I went through my contacts making sure they were all added to my 'Friends' group as I think this may have something to do with what events show and what not but it doesn't seem to help.

What gives? What am I doing wrong or what options should I be looking for to correct this? I've already missed a couple anniversaries and b-days a result and it's frustrating because when I realize I missed it I go to my contacts and there it is listed within the contact info but it never displayed in the calendar for some reason.